Conventional internal combustion engines and air compressors utilize separate valves for controlling the inlet gas and the exhaust gas from each combustion or compression chamber. Each of the valves is reciprocally mounted on the head of a valve in head engine and in the block of a L-head engine. Valve springs are used to hold the valves in their closed positions. A cam shaft and separate rocker arms are used to sequentially open and close the intake and exhaust valves. The exhaust valve is subjected to high temperature exhaust gas that is purged from the combustion chamber. Over a period of time, the exhaust valves deteriorate and burn. The size of the intake and exhaust valves is limited, as they must open into the top of the combustion chamber. The fuel and air mixture is not introduced into the center portion of the chamber, nor is the exhaust gas exhausted from the central area of the chamber. This reduces the charging and purging efficiencies of the engine. The concentric intake and exhaust valve assembly of the invention is designed to alleviate the disadvantages of the separate intake and exhaust valves of an internal combustion engine.